Researchers on Gender Identity Disorder from different countries have reported an increase in the prevalence of GID during the last few decades, as well as changes in the sex ratio of male to female (MTF) and female to male (FTM) GIDs. The aim of this article is to estimate the prevalence and sex ratio of GID in Iran during 2002 to 2009.

All psychiatric records of subjects referred to the Tehran Psychiatric Institute from April 2002 to March 2009 with a diagnosis of GID by two independent reviewers, were assessed. Prevalence of GID was calculated based on the ratio of the total number of identified subjects to the total population aged between 15 and 44 years old.

281 GID subjects with mean age 24.74 at first visit, were studied. The prevalence of MTF and FTM GID was calculated as 1:145,000 and 1:136,000, respectively, and the sex ratio of MTF to FTM GID was 0.96:1. The majority of subjects (229 cases, 81.5%) reported first obvious signs of GID in their childhood and 27 (9.6%) at 14–18 years old. FTM GID subjects showed less obvious childhood signs of GID than MTF GID.

The sex ratio of GID near 1:1 in Iran may indicate that fewer MTF GID subjects seek help in Iran than other countries. We assume that the exact prevalence would be much higher and active prevalence in future reports would be much higher.